1. Field of the Invention
The present invention is directed to a new process for making a hydrocarbyl vinyl ketone. Hydrocarbyl vinyl ketones, especially the most commercially significant of this class of compounds, methyl vinyl ketone, have commercially significant applications. Among these applications are their use as monomers in the copolymerization of photodegradable plastics. That is, when monomers used in the formation of polyethylene-type plastics are copolymerized with a hydrocarbyl vinyl ketone, i.e., methyl vinyl ketone, the copolymer product, a polyethylene-type plastic, not only possesses the same useful properties as the polyethylene plastic but, in addition, the otherwise non-degradable polyethylene plastic becomes photodegradable. Indeed, the rate of degradation of a copolymer of ethylene and methyl vinyl ketone is six times that of a typical ethylene-carbon monoxide copolymer, the class of ethylenic copolymers recognized as having the highest rate of photodegradability of commercially available ethylene copolymer plastics.
A major inhibiting factor in the commercialization of hydrocarbyl vinyl ketone-containing photodegradable copolymers is the high cost of these ketones. The most commercially important of these ketones, methyl vinyl ketone, is produced commercially by dimerization of acetylene to form vinyl acetylene. Hydration of vinyl acetylene produces methyl vinyl ketone.
In view of the high cost of this process attempts have been made to provide a catalytically induced single step process to reduce the cost of manufacturing this compound. However, these prior art processes have utilized catalysts in which the degrees of conversion and selectivity have not reached the level required for commercial exploitation. Therefore, there is a continuing need in the art to develop a commercially viable process which results in the formation of hydrocarbyl vinyl ketones.
2 Background of the Prior Art
Processes have been developed for the catalytic conversion of hydrocarbyl vinyl ketones. Of these prior art processes those most relevant to the present invention involve the catalytic condensation of a ketone with methanol to produce a hydrocarbyl vinyl ketone. This is a desirable process in that it involves a single step reaction to produce the desirable end product.
Such a process is taught in C.A. Selects, Catalysis, 108 (10), 166978y. This abstract of Japanese Patent Publication 62-273,933 to Mitsubishi Chemical Industries Inc. involves the dehydration-condensation of a ketone having the structural formula RCH.sub.2 COR', where R is hydrogen or alkyl; and R' is alkyl, in the presence of niobium oxide. Specifically, acetone is treated with Nb.sub.2 O.sub.5.2.44 H.sub.2 O at 150.degree. C. for one hour to yield a 14.4% conversion at 91.5% selectivity to methyl vinyl ketone.
Another reference relevant to the present invention is the disclosure of Ueda et al., J. Chem. Soc., Chem. Commun., 39-40 (1984). This paper describes the preparation of methyl vinyl ketone by the catalytic reaction of a mixture of acetone and methanol at atmospheric pressure and elevated temperature in the presence of an iron-magnesia catalyst. The best result of the runs reported in this paper is a 12.1% conversion of acetone to produce methyl vinyl ketone at a selectivity of 54.5%. This reaction is conducted at a temperature of 350.degree. C. and at atmospheric pressure.
Hassouni et al., Stud. Surf. Sci. Catal., 41, 307-315 (1988) sets forth a process for synthesizing methyl vinyl ketone from methanol utilizing a copper, silver or zinc catalyst. In a preferred embodiment this reference discloses the formation of methyl vinyl ketone utilizing a silver on silica catalyst activated with an equimolar amount of potassium carbonate.
Whereas all of the above discussed references employ an oxygen-free atmosphere, Okada et al., Chem. Letters, 333-334 (1973) teaches the formation of methyl vinyl ketone by co-feeding acetone, methanol, oxygen and nitrogen gases in a molar ratio of 1:2.1:2.3:8.86, respectively, in the presence of a catalyst of silver on a silica-magnesia support. The requirement of employing a precious metal catalyst, rather than much cheaper iron, limits the attractiveness of the process of this disclosure.